Direct Current Motor Position Control by a Sliding Mode Controlled Dual Three-Phase AC-DC Power Converter

Direct voltage source (DC) and a DC/DC power converter can be used to control the position, speed or torque of a DC motor. In such an operational condition, a rectifier is needed to have a DC voltage source, if a three-phase voltage source is available only. The objective of this study is to replace a rectifier and DC/DC power converter with one AC/DC power converter such that its output would be equal to the voltage needed for control of DC motor. It is assumed that the control algorithm of a DC motor is selected, which means that the desired output voltage of the AC/DC converter as a time function or function of the motor state is known. First, the sliding mode methodology is applied to control the converter's three branches to make three-phase input current track source voltages multiplied by a time-varying gain. Then the gain is selected such that the converter output voltage is equal to the desired input of the DC motor. It is shown that this condition holds if the time-varying gain satisfies the first-order differential equation, which can be implemented as part of the controller. The application of the Lyapunov theory confirmed that the position regulation process has a stable equilibrium point at the origin and the time gain variation is bounded. The power efficiency is equal to one which is a desirable setting in the proposed controller. A numerical simulation demonstrates the application of the developed control methodology for both constant and time-varying angular position reference.